1. Field of the Invention
This invention relates to a system for inputting the Chinese language via limited number of keys.
2. Description of the Related Art
Among conventionally known methods for inputting Chinese words is one in which Chinese syllables are entered in Pinyin and then converted into Chinese characters. Every Chinese character is composed of a single syllable, which is transcribed into one to six letters of the English alphabet. With a keyboard having 26 keys corresponding to the 26 letters in the English alphabet, the input of a single syllable therefore requires one to six keystrokes.
Chinese phonemes have a dimension of tones. The basic tones in Mandarin Chinese are composed of four types of tones, or first, second, third, and fourth tones. Hereinafter, it is assumed that ones referred to simply as “syllables” include no tonic factor. Syllables including tonic factors will be referred to as “syllables with tones.” According to the method, Chinese characters are converted based on “syllables” or “syllables with tones.”
A Chinese syllable is divided into two parts, an initial corresponding to a consonant and a final corresponding to a vowel. In this connection, a final may include any semivowel (head vowel) preceding its vowel, and any consonant following its vowel. According to another method for input, the initial and final are each input by a single keystroke each so that a total of two keystrokes determine a syllable. The method, however, requires a keyboard having thirty-odd keys for the sake of entering initials and finals.
Aside from the methods using a keyboard with a number of keys as described above, another method has been developed. The method requires only about ten keys, such as those of a numeric keypad. This aims to meet the demands of inputting Chinese words in cellular phones, which have become prevalent in recent years.
In the conventional numeric-key-based input method, a single Chinese character is input by the following manner. The first keystroke selects a group of initials, the second keystroke selects the first letter of a final, and the third keystroke selects final(s). Note that at the third keystroke, some keys are allocated for a plurality of finals each. At the fourth keystroke or after, the user selects a desired one from many Chinese characters whose syllables are defined by selected initials and selected final(s).
However, according to the conventional technology of inputting Chinese characters through some ten keys, three keystrokes are insufficient to define a syllable. That only extracts many alternative syllables. The syllables hence correspond to many characters. Because the number of characters is fatally large, the user must select a desired character from many alternative characters. This procedure is very complicated for the user.
Because the number of syllables used in the standard Mandarin Chinese is around 400, a three-digit sequence number is sufficient to be assigned to every syllable. With this sequence number, another method for input can be presumed. According to the method, three keystrokes, each entering a digit by a numeric key, define a syllable. The method, however, requires the users to memorize every sequence number assigned to the corresponding syllable. This method is out of touch with reality.